The Mediterranean fruit fly (Ceratitis capitata, Wiedemann) is an invasive pest that is widespread in Croatia along the entire Adriatic coast and also occurs sporadically on the continent. It causes the greatest damage and economic losses to tangerine fruit and can also cause significant damage to peaches and figs. The hypothesis of this work was that the different plant hosts in which the Mediterranean fruit fly develops lead to phenotypic variability of the pest, which is crucial for the spread of the pest to new areas and adaptation to different agroecological conditions. The main objective of this work was to determine the variability of the Mediterranean fruit fly in relation to different plant hosts (peach, fig, and tangerine) and locations (breeding sites) where the fly develops. The variability of the populations was studied using the methods of geometric and traditional morphometrics, and the "aspect ratio - AR" of the studied populations was calculated and analyzed. By placing 14 specific points on the wings of the Mediterranean fruit fly and by linear measurements of defined morphological characteristics, 10 populations grown from infected peach, fig and tangerine fruit and sterile populations grown in the laboratory were analyzed. The study led to the following important results: sexual dimorphism in the shape of wings is present in all studied populations, the hosts in which the fly evolved influence the shape and size of the wings and condition their variability, significant variability between sterile and wild populations was demonstrated, the ratio of the wingspan of the studied population refers to the variability due to the diversity of plant hosts. Very low variability between different agroecological conditions (different locations and hosts) was detected, indicating the stability of the genotype and high phenotypic plasticity, which is a prerequisite for the invasiveness and spread of the Mediterranean fruit fly to new areas and plant hosts. As trade and climate change progress, the Mediterranean fruit fly will become an even more significant pest and a serious threat to future agriculture.